Touch detection device, electronic apparatus and touch detection method

Abstract

The present invention relates to a touch detection device, an electronic apparatus and a touch detection method. Each frame of touch related data corresponding to n*m capacitive nodes is obtained by producing n*m coupled signals from encoding operations and subjecting the n*m coupled signals to multiple access accumulation process, common mode suppression process, ADC process and decoding processes. Additionally, touch location information of the n*m capacitive nodes is obtained by acquiring two consecutive frames of touch related data and performing a subtraction operation between the two consecutive frames of touch related data. Therefore, relatively high touch sensing sensitivity is achievable. Before the subtraction operation, common-mode analog voltage amounts subtracted in the common mode suppression process may be not added back for each single frame of touch related data obtained from decoding process. This avoids introduction of errors, as well as a larger circuitry area and increased power consumption.

What is claimed is: 
     
       1. A touch detection method, for detecting a change of capacitance at n*m capacitive nodes formed by m driving channels and n sensing channels, wherein both m and n are positive integers, the touch detection method comprising:
 loading, in each encoding cycle, encoded drive signals onto the individual driving channels, capturing, through the individual sensing channels, n*m coupled signals generated at the individual capacitive nodes, and acquiring one frame of touch related data corresponding to the n*m capacitive nodes by performing multiple access accumulation process, common mode suppression process, analog-to-digital conversion (ADC) process and decoding processes on the coupled signals, wherein the common mode suppression process is performed to adjust n accumulated analog voltages obtained from the multiple access accumulation process into an input range of the ADC process; and 
 obtaining touch location information for the n*m capacitive nodes by acquiring two consecutive frames of said touch related data and performing a subtraction operation between the two consecutive frames of said touch related data, 
 wherein before performing the subtraction operation between the two consecutive frames of said touch related data, common-mode analog voltage amounts subtracted in the common mode suppression process are not added back for each frame of said touch related data. 
 
     
     
       2. The touch detection method of  claim 1 , wherein the two consecutive frames of said touch related data are a frame not associated with a touch event and a frame associated with a touch event respectively. 
     
     
       3. The touch detection method of  claim 1 , wherein each of the common-mode analog voltage amounts is determined by a common-mode component accumulated from the m encoded drive signals in each encoding operation. 
     
     
       4. The touch detection method of  claim 1 ,
 wherein the m encoded drive signals are generated in each encoding operation according to codes generated to be applied to the individual driving channels; 
 the multiple access accumulation process comprises capturing, through the individual sensing channels, the n*m coupled signals generated by the m driving channels at the individual capacitive nodes and obtaining the n accumulated analog voltages by performing multiple access accumulation operations on the coupled signals at the m capacitive nodes of each of the n sensing channels and the m encoded drive signals in each encoding operation; 
 the common mode suppression process comprises subtracting common-mode analog voltage amounts beyond the input range of the ADC process from the n accumulated analog voltages so as to generate n analog voltage signals to be decoded; 
 the ADC process comprises convert the n analog voltage signal to be decoded into n digital voltage signals to be decoded; 
 the decoding process comprises decoding the n digital voltage signals based on the codes applied to the m driving channels so as to generate said one frame of said touch related data for the n*m capacitive nodes. 
 
     
     
       5. The touch detection method of  claim 4 , wherein the one frame of said touch related data for the n*m capacitive nodes is generated by decoding n*k digital voltage signals corresponding to n*k accumulated analog voltages obtained from k encoding operations and n*k multiple access accumulation operations, wherein said decoding process is achieved by performing multiply-accumulate (MAC) operations on the n*k digital voltage signals and the k*m codes applied to the m driving channels in the k encoding operations, wherein k is a positive integer. 
     
     
       6. The touch detection method of  claim 4 , wherein the n accumulated analog voltages are adjusted into the input range of the ADC process by drawing or injecting a current. 
     
     
       7. The touch detection method of  claim 6 , wherein the n analog voltage signals to be decoded within the input range of the ADC process are generated from integrating charges at output nodes of the n sensing channels.